Geology Of Australia

	Geology Of Australia The geology of Australia includes virtually all known rock types, spanning a geological time period of over 3.8 billion years, including some of the oldest rocks on earth. Australia is a continent situated on the Indo-Australian Plate. Components Australia's geology can be divided into several main sections: the Archaean cratonic shields, Proterozoic fold belts and sedimentary basins, Phanerozoic sedimentary basins, and Phanerozoic metamorphic and igneous rocks. Australia as a separate continent began to form after the breakup of Gondwana in the Permian, with the separation of the continental landmass from the African continent and Indian subcontinent. Australia rifted from Antarctica in the Cretaceous. The current Australian continental mass is composed of a thick subcontinental lithosphere, over thick in the western two-thirds and thick in the younger eastern third. The Australian continental crust, excluding the thinned margins, has an average thickness of , with a ran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	Continental Crust Continental crust is the layer of igneous, sedimentary, and metamorphic rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called ''sial'' because its bulk composition is richer in aluminium silicates (Al-Si) and has a lower density compared to the oceanic crust, called ''sima'' which is richer in magnesium silicate (Mg-Si) minerals. Changes in seismic wave velocities have shown that at a certain depth (the Conrad discontinuity), there is a reasonably sharp contrast between the more felsic upper continental crust and the lower continental crust, which is more mafic in character. The continental crust consists of various layers, with a bulk composition that is intermediate (SiO2 wt% = 60.6). The average density of continental crust is about , less dense than the ultramafic material that makes up the mantle, which has a density of around . Continental crust is also less dense ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Arunta Block ''Arunta'' is a genus of cicada in the thophini tribe of the Cicadinae subfamily and is allied to the genus ''Thopha''. Two species have been described, ''Arunta perulata'' and '' A. interclusa''. These are the only Australian cicada species that have adapted to living in mangrove A mangrove is a shrub or tree that grows in coastal saline water, saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evoluti ...s. References Thophini Insects of Australia Cicadidae genera {{Cicadidae-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	Gneiss Gneiss ( ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. Gneiss forms at higher temperatures and pressures than schist. Gneiss nearly always shows a banded texture characterized by alternating darker and lighter colored bands and without a distinct cleavage. Gneisses are common in the ancient crust of continental shields. Some of the oldest rocks on Earth are gneisses, such as the Acasta Gneiss. Description Orthogneiss from the Czech Republic In traditional English and North American usage, a gneiss is a coarse-grained metamorphic rock showing compositional banding (gneissic banding) but poorly developed schistosity and indistinct cleavage. In other words, it is a metamorphic rock composed of mineral grains easily seen with the unaided eye, which form obvious compositional layers, but which has only a weak tendency to fracture ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	Granulite Granulites are a class of high-grade metamorphic rocks of the granulite facies that have experienced high-temperature and moderate-pressure metamorphism. They are medium to coarse–grained and mainly composed of feldspars sometimes associated with quartz and anhydrous ferromagnesian minerals, with granoblastic texture and gneissose to massive structure.D.R. Bowes (1989), ''The Encyclopedia of Igneous and Metamorphic Petrology''; Van Nostrand Reinhold They are of particular interest to geologists because many granulites represent samples of the deep continental crust. Some granulites experienced decompression from deep in the Earth to shallower crustal levels at high temperature; others cooled while remaining at depth in the Earth. The minerals present in a granulite will vary depending on the parent rock of the granulite and the temperature and pressure conditions experienced during metamorphism. A common type of granulite found in high-grade metamorphic rocks of the continent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	Musgrave Block The Musgrave Block (also known as the Musgrave Province) is an east-west trending belt of Proterozoic granulite-gneiss basement rocks approximately long. The Musgrave Block extends from western South Australia into Western Australia. The Musgrave Block is primarily exposed through the actions of the Petermann Orogeny at c. 535-550 Ma, which exhumed the orogenic belt along the Woodroffe Thrust. Geomorphology of Quaternary deposits The Musgrave Block is currently passive geologically, with surficial processes described as residual erosion. The area currently experiences on average less than 150mm (6 inches) of rainfall per annum, which provides little surface runoff and hence virtually no erosion. The landforms of the area are primarily composed of wide calcrete plains, often covered by Pleistocene Age aeolian deposits of sand dunes, sometimes reworked into ephemeral sheetwash fans. Outcrop is rare, restricted primarily to the igneous rocks of the Giles Complex and several gr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Willyama Block {{Disambiguation Willyama may refer to: Electoral district of Willyama, New South Wales, Australia former name of Broken Hill Broken Hill is an inland mining city in the far west of outback New South Wales, Australia. It is near the border with South Australia on the crossing of the Barrier Highway (A32) and the Silver City Highway (B79), in the Barrier Range. It is ... , New South Wales ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]